title: Mutations in GERANYLGERANYL DIPHOSPHATE SYNTHASE 1 affect chloroplast development in Arabidopsis thaliana (Brassicaceae).
abstract: OBJECTIVE
  Within plastids, geranylgeranyl diphosphate synthase is a key enzyme in the isoprenoid biosynthetic pathway that catalyzes the formation of geranylgeranyl diphosphate, a precursor molecule to several biochemical pathways including those that lead into the biosynthesis of carotenoids and abscisic acid, prenyllipids such as the chlorophylls, and diterpenes such as gibberellic acid. •
  
  
  METHODS
  We have identified mutants in the GERANYLGERANYL DIPHOSPHATE SYNTHASE 1 (GGPS1) gene, which encodes the major plastid-localized enzyme geranylgeranyl diphosphate synthase in Arabidopsis thaliana. •
  
  
  RESULTS
  Two T-DNA insertion mutant alleles (ggps1-2 and ggps1-3) were found to result in seedling-lethal albino and embryo-lethal phenotypes, respectively, indicating that GGPS1 is an essential gene. We also identified a temperature-sensitive leaf variegation mutant (ggps1-1) in A. thaliana that is caused by a point mutation. Total chlorophyll and carotenoid levels were reduced in ggps1-1 white tissues as compared with green tissues. Phenotypes typically associated with a reduction in gibberellic acid were not seen, suggesting that gibberellic acid biosynthesis is not noticeably altered in the mutant. In contrast to other variegated mutants, the ggps1-1 green sector photosynthetic rate was not elevated relative to wild-type tissues. Chloroplast development in green sectors of variegated leaves appeared normal, whereas cells in white sectors contained abnormal plastids with numerous electron translucent bodies and poorly developed internal membranes. •
  
  
  CONCLUSIONS
  Our results indicate that GGPS1 is a key gene in the chlorophyll biosynthetic pathway.
authors.affiliation: Indiana University, Department of Biology, 915 E 3rd Street, Bloomington, Indiana 47405 USA.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Ruppel
authors.forename: Kelsey N
authors.initials: KN
authors.lastname: Kropp
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Davis
authors.forename: Arielle E
authors.initials: AE
authors.lastname: Martin
authors.forename: Darron R
authors.initials: DR
authors.lastname: Luesse
authors.forename: Roger P
authors.initials: RP
authors.lastname: Hangarter
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism*; D035264:Flowers / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D018525:Germination / Q000187:drug effects; D018546:Hypocotyl / Q000187:drug effects / Q000254:growth & development; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D010788:Photosynthesis / Q000187:drug effects; D010860:Pigments, Biological / Q000378:metabolism; D010937:Plant Growth Regulators / Q000494:pharmacology; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics; D013696:Temperature
chemical_list: D029681:Arabidopsis Proteins; D010860:Pigments, Biological; D010937:Plant Growth Regulators; D019883:Alkyl and Aryl Transferases; C588179:GGPS1 protein, Arabidopsis
keywords: Arabidopsis thaliana; Brassicaceae; GGPS; MEP pathway; chlorophyll; isoprenoid; methylerythritol 4-phosphate pathway; photosynthesis; variegation